Die for molding plastic material



April 27 1926. n

c. B. WELLSv `DIE FOR HOLDING PLASTIC MATERIAL inal Filed "Jam 11 Orig lli

' other form than circular,

Patented Apr, 2.7, 1925.

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" unire stares rarest Tarifes."

CYRUS B. VELLS, 0F SCENTGN, BENSYLVANXA, ASSGNQR TO THE SSRANTON BUT- TGN COMPANY, OF SCBA'NTON, PENNSYLVANIA, A CQRPORATION OF EENNSYL- VANIA.

To ZZ 'whom t 'may concern.'

lie it known that l, CYRUs B. llliii'ins, a citizen of the United States, residing at Scranton, in the county ot Lackawanna and State ot Pennsylvania, have invented certain new and useful Tmprovements in Dies for f Molding` Plastic `tlaterial, ol' which the ollowing is a specification.

This invention relates to improvements in dies `tor molding flat objects, such as phonograph records, from plastic material con taining a binder which softens with heat and is hard at normal temperatures. Dies for molding this material are usually channeled so that steam .may be circulated through them to heat them while the dies ci a pair are separated, and the cold water may be circulated through them to chill and set the material after it has been pressed between the dies.

Tt is customary to form the die plates ot' steel and to cut the channels in the backs ot the plates; but this is an expensive process, especially when the channels are of any and besides, the corrosive action of the fluids on the machined surfaces of the channel walls causes the ribs between the channels to deteriorate much more rapidly than they would it the channels were ot cast metal.

In carrying out the invention, T provide a die-plate, ot steel, with a liat under surlace and with a flange at its periphery, and

a channel-plate, of cast metal, which is machined on its opposite sides and at its pe`- riphery and adapted to fit {luid-tight within the die-plate. The channels in thechannelplate are preferably formed with walls which diverge from the bottoms of the channels upwardly, and the underside of the dieplate closes the open sides of these channels when the plates are fitted together. Thus, the widest parts of the channels are next to the die-plate and a large surface ol' the latter is exposed directly to the heating and cooling fluids which flow through the channels. The channels may be cast in any desired form, and their walls are not machined. Thus, there is a saving in the cost ct forming the channels, and the unfinished walls of the channels otter Igreater resistance to the corrosive action of the fluids thanv would machined walls, thus prolonging the life of the partitions which support the die plate. Furthermore, the channel-plate Application filed January 11, 1824,.. Serial No. 685,611.

'DTE FOR HOLDING PLASTTC MATERIAL.

Renewed March l0, 1926.

braces the die-plate so that there is less danger of buckling the latter while being calked in place in the die frame.

ln the accompanying drawing, which il lustrates the invention,

Fig. l is a lplan view of a die and die rame embodying my invention, the channels in the channel-plate being shown in dotted lines;

Fig. 2 is a section on and,

Fig. 3 is a plan view of the channel-plate.v Y Referring to the drawing, a represents a die frame adapted lto be secured in a press, l) indicates the die-plate, and o represents a channel-plate interposed between the die plate and the traine. The frame has a circular recess l, adapted to receive the die and channel plates. The die plate b is flat and is made as thin as is practicable, and it is provided with a 'flange 2, adapted to tit duid-tight within the peripheral wall la ol' the recess l. The channel plate 0 maybe 01": cast metal, machined on its opposite sides and at its periphery, and it is adapted to lit fluid-tight within the annular flange 2 of the die-plate with the open sides ot the channels 3 facing the body ot the die-plate. The diesplate thus rests against the ribs 4 and 'forms a closure for the channels. The two plates have central openings which lit fluidtight around the central boss 6 on the frame. .Tfn assembling Vthe parts the channel-plate is pressed into the die-plate and the latter is'thenpressed into the recess in the die frame and'calked in place. The channelthe line 2-2 ot Fie'.

plate has openings 3a extending through it" at certain points inthe channels, and these openings aline with openings 7 in the die lrame which communicates with passage ways 5, bored in the frame, tor conducting water and steam to and from the channels.

Usually, die plates are formed of steel, with channels cut in their under-sides, leav ing ribs integral with the plates. This is expensive, especially when the channels have to be cut in forms other than circular, as, 'for instance,y in the spiral `torni shown in the drawing, and besides, the corrosive action of the steam and water on the machined surfaces ot the channels is destructive ol the dies. The channelvlate in the die of the present invention may be cast with lchannels of any form, saving all machining of the channels, and the metallic oxide on the una finished walls of the channels will resist the corrosive action of the fluids to a much greater extent than will the surfaces of machined walls, thereby prolonging the life of the ribs or partitions between the. channels. As a means of protecting from corrosion the machined surfaces of the die-plate and channel-plate which may be exposed to the fluids, a coating of' copper may be deposited upon the inner face of the former, including its flange, and the surfaces of the lat-ter.

It is to be noted that the channel walls diverge toward the die-plate so that a rela-- tively large area of the die-plate comes in direct contact with the fluids, and the'sleping ribs form a morerigid support for the die-plate than the ribs of the usual form, with parallel sides, cut in the underside of the die-plate.

The structure described also provides a leak-proef joint between the die-plate and the die frame at the flange 2. In order that leakage of steam or water from the channels may take place, the fluid must pass from one of the outer channels between the edge of the channel-plate and the flange 2, thence between the bottom of said flange and the bottom ot' the recess l, and thence upwardly between the outer surface of the flange and the peripheral wall la of the recess l. These parts are all forced together while cold, making a fluid-tight joint. lVhen steam is admitted to the channels, the die-plate and the channel-plate both eX- pand. This causes an outward pressure of' the flange on the die-plate against the peripheral wall. of the recess l, and an outward pressure oft the channel-plate against the inner wall of the flange, thereby keeping a perfect seal between the parts while they are heated.

ln the drawing, the channels are arranged in spiral form, with inlets and outlets arranged as more particularly described in the co-pending application of Sylvester and Wells Serial N o. 661,700, filed September 8, 1923; but. it will be evident that the chaninseafrla nels may take any desired form and that the cost of making the die is not alfected by the form of the channels.

lVhat I claim is:

l. A die for molding plastic material comprising a die body, a channel-plate resting on said body and having channels and intermediate ribs on the. side opposite said body, and' a die-plate resting on said ribs and ses cured to the body. Y

2. A die for molding plastic material comprising a die body, a cast metal channelplate resting on said body and having channels and intermediate ribs on the side opposite said body, and a die plate resting on said ribs and secured to the body.

A die for molding plastic material comprising a die body, a channel-plate resting en said body and having channels and intermediate ribs on the side opposite said body, the side walls oi said channels diverging from the bottoms of the channels, and a die-plate resting on said ribs and secured te the body.

rl. die for molding plastic material comprising a die body, a cast metal channelplate resting on said body, a cast metal channel-plate resting on said body and having channels and intermediate ribs on the side opposite said body, the side walls of said channels diverging from the bottoms of the channels, and a die-plate resting on said ribs and'secured to the body.

5. A die for molding plastic material comprising a die-body having` an annular recess, a die-plate having a flange fitting within said recess, and a channel plate fitting within said flange and having channels closed at one side by the die plate. i

6. A die for molding plastic material comprising a die body having an annular recess, a die-plate having a flange fitting within said recess, and a cast metal channel plate fitting within said flange and having channels closed at one side by the die-plate.

ln testimony whereofl I hereunto aiiix my signature. Y

CYRUS B. VWELLS. 

